The Browning .30 machine guns are very reliable, recoil operated guns.  The most commonly found versions are the M1919A4, followed by the M1919A6, and less frequently the M37.  The 'A4 gun is designed to be fired from the M2 tripod and weighs about 44 pounds.  The 'A6 gun is equipped with a bipod, flash hider, and shoulder stock.  It was origianlly designed for airborne troops and weighs in at 33 pounds.  The M37 gun was designed as a co-axial machine gun for tanks and armored vehicles.  It is capable of both right and left hand feeds. 

 

The main difference between the 'A4 and 'A6 configurations is in the weight of the barrels, the length of the barrel jacket, and muzzle bearing.  Barrels on the 'A4 gun are heavy and designed to be heat sinks for prolonged firing.  Barrels on the 'A6 gun are lighter and contoured.  The 'A6 barrel has  wrenching flats on the end to adjust the headspace when the flash hider is removed.

 

Barrel jackets of the guns differ due to the length of the muzzle bearings.  The 'A4 muzzle bearing supports the end of the heavy barrel and acts as a gas trap and booster for the gun.  The 'A6 jacket is shorter than the 'A4 but has a alonger muzzle bearing.  The bearing is designed to accept a bipod yoke and a conical flash hider.  The bipod is taken from the M1918A2 BAR and has adjustable legs with thumb screws to adjust the leg length.  The quick detachable flash hider has a integral muzzle booster.  All 'A6 guns are found with a carrying handle that attaches to the rear of the barrel jacket.  Some 'A4 guns may be found with the same carrying handle.

 

The M37 gun is the same overall as the M1919A4 gun.  However, some of the internal and external parts are different.  The top cover is redesigned to permint conversion to both right and left hand feed.  It has a two cover releases, similar to that on the larger .50 Browning gun.  The bolt has two cam tracks to allow the feed lever to operate either in left or right feed.  The top of the trunnion block is chrome plated to reduce wear from steel links and the right sideplate is opened up to allow right ammunition feed.  Belt holding pawls and front and rear cartridge stops are easily changed from left to right as needed.  The gun can take a feed chute to feed ammunition from a remotely located ammunition box.

 

The most important feature to keep your .30 Browning working is a straight barrel jacket.  I was having problem with an 'A6 gun that just would not keep firing reliably.  I tried different internal parts and different cover assemblies, all to no avail.  I then removed the barrel jacket.  As I turned it off the trunnion, the end of the jacket wobbled!  Although it looked straight, it wasn't.  I replaced the jacket with a new one and the gun shot like it was new.  Just something to remember if your Browning is having reliability problems.

 

There are some so-called M1919A6 semi-automatic versions of this gun.  These guns are made up from M1919A4 parts.  The difference is the the right sideplate is thicker than the standard gun and internal parts of the gun are modified for semi-automatic fire only.  The 'A6 guns being sold are actually 'A4 guns fitted with the 'A6 shoulder stock, an Israeli bipod conversion for the 'A4 gun, and the post Korean War flash hider designed for the 'A4 gun.  These semi-auto versions of the 'A6 are not the true gun.  However, they do have one feature that the original did not have -- the improved Israeli bipod.  The Israeli bipod pivots to allow the gun to do searching fire, while that of the true 'A6 gun does not.